/Engine/Plugins/Runtime/GameplayAbilities/Source/GameplayAbilities/Public/GameplayEffect.h
Actually applies given mod to the attribute
void ApplyModToAttribute ( const [FGameplayAttribute](API\Plugins\GameplayAbilities\FGameplayAttribute) & Attribute, [TEnumAsByte](API\Runtime\Core\Containers\TEnumAsByte)< [EGameplayModOp::Type](API\Plugins\GameplayAbilities\EGameplayModOp__Type) > ModifierOp, float ModifierMagnitude, const [FGameplayEffectModCallbackData](API\Plugins\GameplayAbilities\FGameplayEffectModCallbackData) * ModData )